Foundations and anchoring for an RV carport
Anchoring is what keeps a large sail attached to the ground. It is also the part of the project most often improvised, usually by someone who assumed the surface they already have is adequate.
This is the one area of the project where substituting what is available at the hardware store for what the manufacturer specified is a genuinely bad idea.
Anchor type is determined by your surface
| Surface | Typical approach | What to watch |
|---|---|---|
| Existing concrete slab | Concrete wedge or expansion anchors into the slab | Slab thickness and condition matter. A thin or cracked slab may not be an adequate anchor point — the supplier will usually specify a minimum. |
| New concrete slab | Anchors set into a slab poured for the purpose | A poured slab is typically the most durable option and often the costliest to prepare. Needs to be sized and positioned before the structure arrives. |
| Asphalt | Longer asphalt-specific anchors | Asphalt softens in heat. Anchor length and type differ from concrete. |
| Bare ground / soil | Driven mobile-home style anchors | Suitability depends entirely on soil. Sandy or waterlogged soil holds an anchor very differently from compacted clay. |
| Gravel | Usually concrete footings at each leg, or a slab | Gravel is generally not an anchor substrate. See below. |
The decision framework
Work through these in order. Each answer constrains the next.
- 01What surface exists at the site today, and is it staying?
- 02What does the manufacturer specify for anchoring on that surface?
- 03Is the structure certified, and does that certification require a particular anchor type or foundation?
- 04Does your jurisdiction require a permit, and does the permit application require engineered drawings or a specified foundation?
- 05Is the site level, and if not, who is levelling it?
- 06Does water drain away from the structure footprint, or toward it?
The third of those questions carries more weight than its position suggests.
Site preparation before anything arrives
A level, accessible, cleared site costs nothing to prepare. A sloped or obstructed one can cost more than the structure. Establish which you have early, because it is the most common source of a project coming in well above the quoted figure.
Consider also how the material gets to the site. Kerbside delivery of long, heavy steel to a property with a narrow approach is a logistics problem that is much cheaper to solve before the truck is booked.
Drainage
Water that runs off a large roof has to go somewhere. If the ground slopes toward the structure footprint, or if the roof discharges onto a surface that erodes, you will be managing that for as long as the structure stands. Deciding where the water goes is part of siting, not an afterthought.
Limitations
What this does not establish
- Anchor counts, embedment depths, or footing sizes. These are engineering values that depend on the specific product, your soil, and your local wind and snow requirements.
- Load ratings for any structure or anchoring arrangement. Those come from the manufacturer’s engineered documentation, not from general guidance.
- Whether the surface you already have is adequate for the structure you are considering. Only the supplier, against their own specification, can confirm that.
Confirm before you buy
- The carport manufacturer or supplier
- What they specify for anchoring on your surface, and any minimum slab thickness or condition they require.
- A local engineer, where one is required
- Footing sizes and anchoring for your soil and local wind and snow requirements, where the engineered documentation does not already cover your site.
- Your local building department
- Whether a permit is required, and whether the application requires engineered drawings or a specified foundation.